Classical cognitive radios change frequency channels when the radio detects that the interference level or other parameters associated with operation can be improved by moving to another frequency. Modern signal processing and multiple antenna technologies, however, allow expanded cognitive operation where receiver algorithms and transmit waveforms can be instantly and dynamically adjusted for operation in a particular environment.
Radio spectrum is a limited resource. A large amount of spectrum is required to deliver services that are associated with modern wireless personal communications. Typical examples are smart phone Internet applications, wireless streaming audio, and video, to mention a few. These services consume large amounts of spectral resources causing both financial and spectrum policy issues.
Typically these services are provided using licensed spectrum. The financial burden from licensing can be defined as a cost of billions of dollars, even for a relatively small amount of spectrum, when compared to freely available unlicensed spectrum. The licensing, however, is required to make sure that current 1G to 4G radio technologies have the coordinated access they require to deliver quality of service that is adequate for an end user application.
Currently in the United States there are several hundred MHz of unlicensed spectrum that can be used for delivering wireless services to consumers, however, traditional radio technologies typically suffer from interference from uncoordinated access from other unlicensed users. A novel radio technology is required that can deliver service while being highly resistant to interference and also creating as little interference as possible to other users in the unlicensed band.